Avoid libaio for usermode

Linux AIO is aonly used by system emulation, so should not be linked into
the userspace emulatior.

Signed-off-by: Paul Brook <paul@codesourcery.com>
diff --git a/configure b/configure
index 87942f4..36d028f 100755
--- a/configure
+++ b/configure
@@ -1579,7 +1579,8 @@
 EOF
   if compile_prog "" "-laio" ; then
     linux_aio=yes
-    LIBS="$LIBS -laio"
+    libs_softmmu="$libs_softmmu -laio"
+    libs_tools="$libs_tools -laio"
   else
     if test "$linux_aio" = "yes" ; then
       feature_not_found "linux AIO"